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- Physics, Mechanical, Engineering (2)
- Publications (2)
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- Direct (1)
- Effective properties (1)
- Electron current (1)
- Energy distribution (1)
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- Length (1)
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- Photoluminescence (1)
- Physics (1)
- Porous silicon (1)
- Raman spectroscopy (1)
- Random orientation fibers (1)
- Rotor (1)
- Semiconductor lithography (1)
- Silicide formation (1)
- Silicon field emitters (1)
- Simulation (1)
- Spectroscopy (1)
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Articles 1 - 10 of 10
Full-Text Articles in Physics
Driven Front And Interface Of A Fluid-Flow Model In 2+1-Dimensions, Michael J. Leaseburg, Ras B. Pandey
Driven Front And Interface Of A Fluid-Flow Model In 2+1-Dimensions, Michael J. Leaseburg, Ras B. Pandey
Faculty Publications
Computer simulations are performed to study the motion of the front and the growth of the interface width in a model of fluid flow driven by a biased field in 2+1 dimensions. The initial motion of the front is diffusive, which is followed by a nondiffusive power-law behavior in the long-time regime; the power-law exponent is nonuniversal, varying with the strength of the driven field. The growth of the interface width saturates in the asymptotic time regime. The saturated width W scales with both the driven field B as well as the transverse length L of the sample, leading to …
Raman Spectroscopic Study Of The Formation Of T-Mosi2 From Mo/Si Multilayers, Ming Cai, David D. Allred, A. Reyes-Mena
Raman Spectroscopic Study Of The Formation Of T-Mosi2 From Mo/Si Multilayers, Ming Cai, David D. Allred, A. Reyes-Mena
Faculty Publications
We have used Raman spectroscopy, large- and small-angle x-ray diffraction spectroscopy of sputter-deposited, vacuum-annealed, soft x-ray Mo/Si thin-film multilayers to study the physics of silicide formation. Two sets of multilayer samples with d-spacing 8.4 and 2.0 nm have been studied. Annealing at temperatures above 800 °C causes a gradual formation of amorphous MoSi2 interfaces between the Si and Mo layers. The transition from amorphous to crystalline MoSi2 is abrupt. The experimental results indicate that nucleation is the dominant process for the early stage and crystallization is the dominant process after nucleation is well advanced. In the thicker multilayer, a portion …
Emitted Current Instability From Silicon Field Emission Emitters Due To Sputtering By Residual Gas Ions, W.I. Karain, Larry V. Knight, David D. Allred, A. Reyes-Mena
Emitted Current Instability From Silicon Field Emission Emitters Due To Sputtering By Residual Gas Ions, W.I. Karain, Larry V. Knight, David D. Allred, A. Reyes-Mena
Faculty Publications
We have fabricated arrays of silicon field emitters using semiconductor lithography techniques. The density of the tips was 10^5/cm^2. The maximum current that can be extracted from each emitter is limited by resistive heating. We have investigated how the electron current emitted changes under constant applied voltage. We found that the current is very sensitive to the vacuum conditions. We attribute this to sputtering of the emitters due to ionized residual gas molecules. The poorer the vacuum, the higher the instability in the current. We studied this phenomenon at 10^6 and 10-x Torr. The model of two concentric spherical shells …
Mesostructure Of Photoluminescent Porous Silicon, David D. Allred, F. Ruiz, C. Vázquez-López, Jesus González-Hernández, G. Romero-Paredes, R. Peña-Sierra, G. Torres-Delgado
Mesostructure Of Photoluminescent Porous Silicon, David D. Allred, F. Ruiz, C. Vázquez-López, Jesus González-Hernández, G. Romero-Paredes, R. Peña-Sierra, G. Torres-Delgado
Faculty Publications
Scanning electron microscopy, atomic force microscopy, and Raman spectroscopy were used to characterize the microstructure of photoluminescent porous silicon (PS) layers formed by the anodic etching (HF:H2O:ethanol), at various current densities, of p-type (100) silicon wafers possessing resitivity in the range 1-2 Ω cm. Existing models for the origin of luminescence in PS are not supported by our observations. Cross-sectional as well as surface atomic force micrographs show the material to be clumpy rather than columnar; rodlike structures are not observed down to a scale of 40 nm. A three-dimensional model of the mesostructure of porous silicon is discussed. Room-temperature …
Absence Of Size Dependence Of The Kondo Resistivity, V. Chandrasekhar, P. Santhanam, N. A. Penebre, Richard A. Webb, H. Vloeberghs, C. Van Haesendonck, Y. Bruynseraede
Absence Of Size Dependence Of The Kondo Resistivity, V. Chandrasekhar, P. Santhanam, N. A. Penebre, Richard A. Webb, H. Vloeberghs, C. Van Haesendonck, Y. Bruynseraede
Faculty Publications
We have measured the low temperature resistivity of AuFe wires in the dilute magnetic impurity limit as a function of wire width, temperature, and magnetic field. When the width dependence of the electron-electron interaction contribution to the resistivity is taken into account, the temperature dependence of the remaining Kondo contribution to the resistivity of all samples with the same impurity concentration is identical. Similar behavior is observed for the magnetic field dependent resistivity. Thus, the Kondo contribution to the resistivity is independent of width down to 38 nm, much smaller than the Kondo length ξK=ħvF/kB …
Listening To Free Fall With The Macrecorder, Thomas O. Callaway, James C. Dennis
Listening To Free Fall With The Macrecorder, Thomas O. Callaway, James C. Dennis
Faculty Publications
No abstract provided.
Direct Simulation Monte Carlo For Thin Film Bearings, Alejandro Garcia, B. Alder, F. J. Alexander
Direct Simulation Monte Carlo For Thin Film Bearings, Alejandro Garcia, B. Alder, F. J. Alexander
Faculty Publications
The direct simulation Monte Carlo (DSMC) scheme is used to study the gas flow under a read/write head positioned nanometers above a moving disk drive platter (the slider bearing problem). In most cases, impressive agreement is found between the particle-based simulation and numerical solutions of the continuum hydrodynamic Reynolds equation which has been corrected for slip. However, at very high platter speeds the gas is far from equilibrium, and the load capacity for the slider bearing cannot be accurately computed from the hydrodynamic pressure.
Microscopic Simulation Of Dilute Gases With Adjustable Transport Coefficients, Alejandro Garcia, F. Baras, M. Malek Mansour
Microscopic Simulation Of Dilute Gases With Adjustable Transport Coefficients, Alejandro Garcia, F. Baras, M. Malek Mansour
Faculty Publications
The Bird algorithm is a computationally efficient method for simulating dilute gas flows. However, due to the relatively large transport coefficients at low densities, high Rayleigh or Reynolds numbers are difficult to achieve by this technique. We present a modified version of the Bird algorithm in which the relaxation processes are enhanced and the transport coefficients reduced, while preserving the correct equilibrium and nonequilibrium fluid properties. The present algorithm is found to be two to three orders of magnitude faster than molecular dynamics for simulating complex hydrodynamical flows.
Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu
Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu
Faculty Publications
No abstract provided.
Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu
Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu
Faculty Publications
A ressessment of existing theories for calculating the strength of random and quasi-random fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common …